From owner-freebsd-hackers Sun Jul 14 04:30:26 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id EAA10017 for hackers-outgoing; Sun, 14 Jul 1996 04:30:26 -0700 (PDT) Received: from gateway.sequent.com (gateway.sequent.com [138.95.18.1]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id EAA10002 for ; Sun, 14 Jul 1996 04:30:21 -0700 (PDT) Received: from kiska.svc.uk.sequent.com (kiska.svc.uk.sequent.com [158.84.31.99]) by gateway.sequent.com (8.6.13/8.6.9) with ESMTP id EAA09072; Sun, 14 Jul 1996 04:24:56 -0700 Received: from lonsqnt.uk.sequent.com (localhost [127.0.0.1]) by kiska.svc.uk.sequent.com (8.6.13/8.6.10) with ESMTP id LAA09015; Sun, 14 Jul 1996 11:29:10 +0100 To: Michael Hancock cc: Warner Losh , Bruce Evans , matt@lkg.dec.com, freebsd-hackers@FreeBSD.ORG, tech-kern@NetBSD.ORG Subject: Re: Some interesting papers on BSD ... In-reply-to: Your message of "Sun, 14 Jul 1996 17:52:51 BST." Date: Sun, 14 Jul 1996 11:29:05 BST Message-ID: <9004.837340145@lonsqnt.uk.sequent.com> From: Jan-Simon Pendry Sender: owner-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk % > : spl is probably fundamentally wrong for SMP. I haven't thought much % > : about what to use instead. % > % > The Solbourne people might disagree with you. As might the VMS % > Digitial people. Both groups used a scheme where you would raise the % > spl *AND* grab access locks to data structures (I think the latter was % % It's the quick and dirty route to getting an SMP version out the door % under budgetary or market timing constraints. % % To do it right, sections of code have to be rewritten to make the code as % parallel as possible. % % Caching also works very differently with multiple CPU's. unless you redesign the interrupt mechanism, you still have to raise spl levels for locks on data structures that can be accessed from interrupt handlers (or timeouts etc). if the cpu runs at the normal spl, it may end up taking an interrupt and then trying to lock a structure that the interrupted thread on the cpu had already locked. jan-simon.